1. Field of the Invention
This invention relates to a method and apparatus for generating x-ray photon radiation and, more particularly, for generating x-ray photon radiation from a plasma source.
2. Description of the Related Art
Photons are emitted when electrons return from a higher energy orbit to a lower one. A high brightness (intensity) photon source can be produced if the lower orbit electrons can be excited to a higher energy orbit at high efficiency. One way to do this is to use high temperature and high density plasma.
Several plasma x-ray sources have been previously developed. These plasma sources can be divided into non-laser plasma sources and laser plasma sources. The problems associated with non-laser plasma x-ray sources are (1) a very large source spot, such as in a gas puff z-pinch x-ray source, which limits resolution in an imaging application; or, (2) a short life time, such as in a vacuum spark x-ray source, where the source anode, bombarded by negatively charged particles, is subjected to extremely high temperatures which may evaporate the anode after a few hundred flashes.
Problems associated with a laser plasma x-ray source include massive structure and high cost. In addition, the laser plasma x-ray source is less versatile in that it produces only soft x-rays which have relatively low energy in a range from about 0.25-10 keV. Soft x-rays cannot meet the requirements of some applications, for example, in non-destructive evaluation of materials and machined structures where a large penetration depth of x-ray is needed.